1. Field of the Invention
The present invention relates to a hemming device and a hemming method for hemming a plate-like workpiece.
2. Description of Related Art
Conventionally, while the inner panel and the outer panel, for example, of a rear door which are the panel members of a vehicle are assembled with each other, hemming for hemming the peripheral edge of the outer panel and superposing the hemmed peripheral edge thereof on the peripheral edge of the inner panel is carried out by a hemming device shown in FIG. 1 which is a side view of the hemming device and in FIG. 2 which is a plan view thereof.
In this hemming device, a workpiece W is positioned and set on a hemi die 3 disposed on a base 1 in a state in which the outer panel 5 is provided below an inner panel 7. The inner panel 7 is positioned and fixedly positioned on this upper position by a positioning jig 9 which is vertically moved by a cylinder 8. The workpiece W thus positioned is provisionally hemmed by a plurality of pre-hemming punches 11 provided around the workpiece W and then finally hemmed by hemming punches 13 provided to correspond to the respective pre-hemming punches 11.
The hemming punches 13 and the pre-hemming punches 11 are actuated by hydraulic cylinders 19 rotatably supported by brackets 15 fixed to the base 1 through rotation support shafts 17, respectively. That is to say, if the hydraulic cylinder 19 is driven, the piston rode 21 of the cylinder 19 advances and a punch holder 23 having hemming punches 13 on a tip end thereof rotates about a rotation support shaft 27 in an arrow A direction relative to the bracket 25 on the base 1, whereby the final hemming is carried out by the hemming punches 13.
On the other hand, the pre-hemming punches 11 carry out provisional hemming prior to the hemming by the hemming punches 13 by advancing to the workpiece W by the rotational operation of the punch holder 23 in the arrow A direction and then retreat. That is to say, using one hydraulic cylinder 19, the provisional hemming by the pre-hemming punches 11 and the final hemming by the hemming punches 13 are carried out in succession.
As for working units Us and Uc each consisting of the hemming punch 13, the pre-hemming punch 11, the hydraulic cylinder 19 driving the respective punches and the like, a total of eight, i.e., four working units (Us) corresponding to the linear portion of a generally rectangular rear door and four working units (Uc) corresponding to the corner portions of the rear door, are provided so as to hem the entire periphery of the workpiece W as shown in FIG. 2.
However, the above-stated conventional hemming device has the following disadvantages:
(1) The hemming device is constituted to carry out hemming by the rotation of each punch holder 23. Due to this, all of the eight working units cannot be actuated simultaneously so as to prevent adjacent working units from interfering with one another. Instead, it is necessary to use different operation timing among the respective working units such as, for example, to actuate the working units Uc for corner portions prior to the working units Us for the linear portions. As a result, the cycle time of the working operation becomes disadvantageously longer.
(2) If the shape of the workpiece W is such that the vertical position of a region to be hemmed by one working unit changes along the peripheral edge portion in FIG. 1, the approach angles of the pre-hemming punches 11 with respect to the workpiece W become uneven. This makes provisional hemming accuracy unstable and degrades working quality.
(3) It is necessary to set the direction in which the hemming punch 13 applies hemming pressure to be perpendicular to the surface of the workpiece W and to appropriately set the approach angles of the pre-hemming punch 11 with respect to the workpiece W. Due to this, it is difficult to standardize hemming punches and the hemming punches should be set in accordance with the shape of each workpiece, thereby pushing up cost.
(4) To work a corner portion, a dedicated small working unit Uc is required. The number of overall working units increases accordingly to thereby push up cost.
(5) The stroke of the hydraulic cylinder 19 tends to be long, which makes the overall working unit large in size. If the hydraulic cylinder 19 is disposed to be closer to the base 1 so as to shorten the stroke, then a driving force intensifies to thereby make the hydraulic cylinder 19 larger in size.
(6) The hemming device is constituted such that hemming pressure is generated by rotating the punch holder 23 by the hydraulic cylinder 19 attached to the base 1 through the bracket 15 and received on the base 1 side. This requires the rigidity of the base 1 and the overall working unit, making the overall working unit large in size.
Meanwhile, the conventional hemming device stated above employs the positioning jig 9 to position the inner panel 7. Since this positioning jig 9 has a relatively long vertical stroke, the accuracy thereof deteriorates and the size is made large. Besides, it is necessary to provide a transport device dedicated to the transport of the workpiece such as a belt conveyer in addition to the positioning jig 9 so as to set the workpiece W on the hemming die 3. This makes the entire facility large in size.
It is, therefore, an object of the present invention to suppress cost increase by decreasing the number of working units, preventing each working unit from becoming large in size, and to reduce processing time by allowing the respective working units to simultaneously operate without interfering with one another even if the units are adjacent each other.
It is also an object of the present invention to improve workpiece positioning accuracy, to dispense with a transport device dedicated to the transport of a workpiece and to thereby make entire facility small in size.
To obtain the above-stated objects, there is provided a hemming device comprising: a hemming punch provided on an upper portion of a C-shaped frame; a hemming die provided on a base on which the C-shaped frame is disposed, and vertically movable to be adjacent to and away from the hemming punch; and a driving section provided between said hemming die and a lower portion of the C-shaped frame and raising said hemming die to hem a workpiece set on said hemming die.
According to the hemming device thus constituted, by raising the hemming die using the driving section, the workpiece on the hemming die is hemmed between the hemming die and the hemming punch on the upper portion of the C-shaped frame.
Further, to obtain the above objects, there is provided a hemming method comprising: setting a workpiece on a hemming die vertically movably provided on a base in a state while a C-shaped frame and a pre-hemming punch provided at the C-shaped frame are retreated; advancing the C-shaped frame and the pre-hemming punch provided at the C-shaped frame; raising the hemming die by a driving section provided between a lower portion of the C-shaped frame and the hemming die, and conducting provisional hemming to the workpiece by the pre-hemming punch; retreating the pre-hemming punch; and raising the hemming die by the driving section, and conducting hemming to the workpiece by the hemming punch provided on an upper portion of the C-shaped frame.
According to the above-stated hemming method, by the raising operation of the hemming die by driving the driving section above the C-shaped frame, the workpiece is hemmed by the pre-hemming punch and the hemming punch provided on the C-shaped frame side.
Moreover, to obtain the above objects, there is provided a hemming device for hemming a peripheral edge of a workpiece using a lower die, on which the workpiece is set, and an upper die arranged above the lower die, the hemming device comprising: a hand mount provided on the lower die side; a workpiece grip hand positioning and gripping the workpiece, and positioned and mounted on the hand mount so as to position and set the workpiece on the lower die; and a hand transport section detachably holding the workpiece grip hand.
According to the hemming device thus constituted, the workpiece grip hand which positions and grips the workpiece is positioned and mounted on the hand mount while being held by the hand transport section. At this moment, the workpiece is set on the lower die and hemmed by the lower die and the upper die while releasing the holding of the workpiece grip hand by the hand transport section.
Furthermore, to obtain the above objects, there is provided a hemming method comprising: holding and transporting a workpiece grip hand positioning and gripping a workpiece by a hand transport section; mounting the workpiece grip hand on a hand mount so as to set the workpiece on the lower die; and hemming the workpiece by the lower die and an upper die located above the lower die.
According to the above-stated hemming device, the workpiece grip hand held by the hand transport section functions to both position and grip the workpiece and transport the workpiece.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.